Alternative N Fertilizer Management Strategies Effects on Subsurface Drain Effluent and N Uptake

Abstract

Demonstrating positive environmental benefits of alternative N fertilizer management strategies, without adversely affecting crop growth or yield, was a major goal for the Midwest Management Systems Evaluation Areas (MSEA) program. Our project objectives within this program were to quantify the effects of split-and single-N fertilization strategies on NO3-N concentration and loss in subsurface drain effluent and N accumulation and yield of corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. The study was conducted on glacial till derived soils in northeast Iowa from 1993 through 1995 using no-till and chisel plow tillage treatments. One-third of the 2,611 effluent samples had NO3-N concentrations greater than 10 mg L-1. Split applying fertilizer N based on pre-sidedress soil nitrate test (PSNT) results significantly increased corn yield for both tillage treatments in the extremely wet 1993 without increasing NO3-N loss in drain effluent. Increased grain yield also resulted in significantly more N removal. When fertilizer N was applied based on the PSNT, no-till and chisel treatments had similar NO3-N losses and concentrations. Average flowweighted NO3-N concentrations in drain effluent were not increased when larger amounts of fertilizer were applied based on PSNT. However, prior crop and tillage practices and differences in drain flow volume caused significant differences in NO3-N losses and concentrations. These results suggest that spatial differences in flow volume are a major factor determining NO3-N loss in drainage effluent. Significant differences suggest that combining no-tillage practices with split N fertilizer management strategies can have positive environmental benefits without reducing corn yield.

Cropping System Effects on No3–n Loss With Subsurface Drainage Water

“…The late-spring UAN applications were determined based on the late-spring NO 3 -N test (LSNT) developed for Iowa soils (Blackmer et al, 1989), in addition to 30 kg-N ha -1 applied with the corn planter (Bjorneberg et al, 1998). Based on LSNT, UAN was injected to increase the soil NO 3 -N concentrations in the top 300 mm of the soil profile to 25 mg kg -1 .…”

“…The NO 3 -N loss with subsurface drainage water in kg-N ha -1 was calculated by multiplying the NO 3 -N concentrations in mg L -1 with the drainage effluent in mm and dividing it by 100 (conversion factor) for each interval of sampling (i.e., two times per week). The cumulative NO 3 -N loss and drainage effluent for the entire monitoring season were used to calculate the flow-weighted average NO 3 -N concentrations for each year (Bjorneberg et al, 1998).…”

“…ater drained from croplands in the midwestern parts of the U.S. has been identified as a potential nonpoint source of surface water contamination with nitrate-nitrogen (NO 3 -N), which may have adverse effects on human and animal health (Kanwar et al, 1999;Jaynes et al, 1999;Cambardella et al, 1999;Bjorneberg et al, 1998;Gentry et al, 2000). Recently, the development of a hypoxic zone in the Gulf of Mexico has also been attributed to the increased loadings of nitrates in the Mississippi River (Rabalais et al, 1999).…”

“…The time between supply of the available form of nitrogen in the soil and plant uptake of N can affect the leaching of NO 3 -N. Bjorneberg et al (1998) reported that much of the pre-plant N fertilizer and mineralized N in the soil may have denitrified or leached from the soil profile before it could be used by the corn. Milburn and Richards (1994) and Bjorneberg et al (1996) reported that 50% to 85% of the annual drain flow and 45% to 85% of the annual NO 3 -N losses occurred when crops were not actively growing.…”

“…The duration, during which soil nitrates are prone to leaching, can be changed by N application methods. The split application of N fertilizer based on late-spring nitrate test (LSNT) can reduce the leaching time and can increase the plant uptake of N. A single pre-planting application of N fertilizer can provide more time for its leaching, particularly when applied at the time of less N requirement by the plants (Blackmer et al, 1989;Meisinger et al, 1992;Bjorneberg et al, 1998). These studies, however, have not reported the integrated effects of tillage when combined with single or split N applications for corn-soybean rotation plots on the leaching losses of NO 3 -N with subsurface drainage water.…”